The journey of thousands of migrants to Australia in the early 19th Century are etched in sandstone at Australia's oldest quarantine station in Sydney.

For more than a century, their stories have remained untold, but a team of archaeologists and historians is now working on uncovering the secrets locked in the stone.

The idyllic scene at North Head in Manly on Sydney Harbour's foreshore today is far removed from what it was used for in the early 19th Century.

Then it operated for 157 years as Australia's first quarantine station.

Newly-arrived migrants suspected of carrying an infectious disease - such as smallpox or typhoid - were isolated for 40 days or longer at the site.

Some used the time to make inscriptions in the sandstone cliffs and rock ledges on the shoreline.

Now, a project is underway to uncover the stories behind those inscriptions.

Archaeologist Annie Clarke from the University of Sydney says it's by far the largest, most concentrated group of historical inscriptions in Australia.

"There was network of quarantine stations around Australia as well. This place is unusual in that there are these inscriptions. The others don't have these kinds of records really of people marking their presence.

"It's because we've got sandstone that people can actually chip away at. You know other places aren't in this kind of landscape."

More than 1000 inscriptions dating back to the 1820s are scattered throughout the site, with many yet to be recorded.

The inscriptions range from names and initials to medallion-like carvings and commemorative plaques.

The team that includes Annie Clarke is working under a three-year government grant to uncover the stories told in the rock.

She says it's uncovering interesting details of sea-borne migration to Australia during the early 19th Century.

"It tells us about kind of multicultural migration to Australia. From the 19th Century onwards. I think it shows us the multi-varied ethnicity of ship crews.

"It was not clear who were passengers and who were crew yet. We'll work that out. But there are many non-Anglo names. So it's not just a story of English migration. You've got Chinese, you got Japanese crews coming through. There are names that appear to be Portuguese and Arabic of course as well.

"One of the interesting things is, as we do more research on the ships and shipping companies, it's clear that Australia was really globally connected in the 19th Century that again it's not just British ships and British shipping companies. You've got shipping companies that operate out of China."

The team is using 3D laser technology, historical photographs and records to piece together the stories before the sandstone wears away the inscriptions completely.

But the stories are also being slowly unravelled with the help of descendants of the migrants who made the inscriptions.

Max Howie is one of them.

His great-grandfather John Howie was a stone mason from Scotland who migrated to Australia with his wife and his son following the collapse of the city bank of Glasgow in 1879.

"Sailing around the globe below 40 degrees latitude it wouldn't be exactly pleasant, I can tell you. I've done it myself. It's a lonely passage out from Scotland to here.

"He lost his son at sea. And according to the death certificate - and we just found it - from the Scottish Mormon Church saying his son died on 1 May 1880 at two years (of age) of bronchitis."

John Howie and his brother Archie went on to build iconic buildings in Sydney's CBD, such as the Mitchell Library, the NSW Art Gallery and the GPO tower in Martin Place.

But their earliest work in the country remains two inscriptions at the Quarantine Station.

Annie Clarke says one of these inscriptions in particular sparked the interest of the team.

It's located on a rock face three metres above sea-level.

"When we looked at it we said: who is missing? Well the person who is missing is the surgeon Mr Pringle Hughes. So why is he missing? Often the doctor is on these ones, the 19th Century ones. So Miss Jones being the matron in charge of the morals of the girls, the single women. I don't think she did such a good job because apparently the surgeon was found with not just one, but two of the single Catholic women not just on the ship, but also at the quarantine station, so they say. Apparently the girls were on their knees they were praying, so they said. So I'm not sure if that is true or not. In a sense it is kind of illustrative of the back story that sits behind many of these inscriptions."

The stories behind the other inscriptions are less clear.

But Dr Clarke says inscriptions written in different languages reflect a variety of cultural practices.

"It's very formal inscriptions here. Both the Chinese, very formal, as you would see other Chinese script and calligraphy. And they're finely painted. And the European ones really pick up on the kinds of things you see churches and memorials. So people are actually doing things in relation to their cultural practices. As archaeologists, that's one of the things we were really drawn to."

DEATH AND THE QUARANTINE STATION

More than 13,000 people were quarantined at North Head between 1828 and 1984.

Many succumbed to illnesses without ever leaving the quarantine station.

However, Dr Clarke says death is not a dominant theme in the inscriptions.

"About 580, 600 people died, buried in three cemeteries. But that is actually quite a small percentage of the people who were here.

"So it is not so much about death. Maybe it's about presence and survival. And commemorating as much as it is about death."

That's certainly how the site is seen by one descendant of Irish migrant William Kennedy.

Rob Young had known of the existence of an inscription by Kennedy at North Head.

But he wasn't able to get to see it until the 1980s, when the site was opened to the public for the first time, after it became part of Sydney Harbour National Park.

"He was my mum's dad. And it was only up until 1987 we could go up and look at quarantine station base and actually see the inscription that he made. And I was delighted to take my mum and she was delighted and unfortunately, she passed away soon after. But it was just good to be able to do it.

"The only thing which I'm sort of proud of I suppose is the fact that the Kennedys, my mother's side of the family, have something which will be there for a long, long time, which is part of the history of Australia I guess."

William Kennedy had been returning to Sydney from an overseas business trip when the ship he was on, the RMS Niagara, was placed in quarantine for four weeks.

Rob Young's wife and former teacher, Margaret, has compiled the story of what happened.

"We do have a certificate of his being given permission to go to America on business, which is what he did, he was the chief engineer of Australian Glass Manufacturers. He went over with his boss, AJ Smith, to America to do some research into glass making. So it was a business trip basically. And I don't believe he was ill. He and his boss evaded the germs on the ship by pulling their bedding up onto the deck, and sleeping outside and living outside on the ship as far as they could."

It's stories like William Kennedy's and John Howie's that Annie Clarke and other members of her team are aiming to document in an online database for the public.

"I'm sure some of the back stories behind some of the voyages, yeah, there will be kind of unknown and unusual histories revealed. It's a history of the ordinary person in many ways. It's not the rich and famous. It's the history of the working people and ordinary migrants to Australia. And I think that is what makes it, kind of, you know really attractive as history, getting a whole different layer of history. History from the ground up."